1. Field of the Invention
The present invention relates to touch panels to be used for operation of various types of electronic equipments and manufacturing method for the same.
2. Background Art
In recent years, optically transparent touch panels are installed on the front surface of display devices such as liquid crystal display in a variety of electronic equipment such as mobile phones and car navigation systems. Through touch panels, visual identification of characters and symbols displayed on the screen can be made. Also, through touch panels, selection of the characters and the symbols can be made. Furthermore, touch panels are operated by depressing them with a finger or a thing such as a dedicated pen. With this operation, each function of electronic equipment can be switched. Accordingly, touch panels that suffer less wrong operation and are easy to operate are required.
A description of such a conventional touch panel will be given referring to FIG. 4.
FIG. 4 is a cross-sectional view of a conventional touch panel. In FIG. 4, optically transparent upper substrate 101 is in the form of a film. Optically transparent lower substrate 102 is formed of glass and the like. Optically transparent upper conductive layer 103 made of indium tin oxide and the like is formed at the lower surface of upper substrate 101. Optically transparent lower conductive layer 104 made of indium tin oxide and the like is formed at a top surface of lower substrate 102.
In addition, optically transparent elastic layer 105 made of silicone rubber, urethane rubber and the like is formed at a space between upper conductive layer 103 and lower conductive layer 104. Two or more conductive wires 106 made of nickel, stainless steel or the like are disposed in a manner vertically oriented and buried inside elastic layer 105. Bottom ends of conductive wires 106 are in contact with lower conductive layer 104. A predetermined space is provided between top ends of conductive wires 106 and upper conductive layer 103.
Furthermore, a pair of upper electrodes (not shown) is formed at both ends of upper conductive layer 103. A pair of lower electrodes (not shown) is formed at both ends of lower conductive layer 104 in a direction orthogonal to the upper electrodes. Touch panel 100 is constructed in this way.
Electronic equipment (not shown) is constructed by disposing touch panel 100 constructed in this way on the front surface of a liquid crystal display device (not shown), for example. At the same time, the pair of upper electrodes and the pair of lower electrodes are connected to an electronic circuit (not shown) of the electronic equipment, respectively.
In the above configuration, a top surface of upper substrate 101 is depressed with a finger or a thing such as pen in the direction of arrow X while visually confirming what is displayed on the liquid crystal display device, for example, on a back of touch panel 100. With this operation, upper substrate 101 and elastic layer 105 are bent, and that part of upper conductive layer 103 which is depressed and the top ends of conductive wires 106 come into contact together. When upper substrate 101 is further depressed, conductive wires 106 are bent. At this result, upper conductive layer 103 and lower conductive layer 104 are electrically connected via conductive wires 106.
And, an electrical power supplied from the electronic circuit is sequentially fed to the upper electrodes and the lower electrodes. The electronic circuit detects a location of depression based on a voltage ratio detected by the upper electrodes and a voltage ratio detected by the lower electrodes. With this, switching of various functions of the electronic equipment is performed.
Also, when depressing force on upper substrate 101 is released, upper substrate 101 returns to an original form by elastic restoring forces of upper substrate 101 and elastic layer 105. With this, upper conductive layer 103 is detached from the top ends of conductive wires 106.
Such a conventional touch panel 100 as above described is disclosed in Unexamined Japanese Patent Publication No. 1984-188726, for example.